The present disclosure generally relates to a signal processing circuit, and more particularly, to a signal processing circuit utilized in a multiple-antenna device.
In wireless communications, the utilization of multiple antennas may effectively enhance the system performance. The antennas may be used to provide the antenna diversity, the multiple-input-multiple-output (MIMO) function, etc. For example, IEEE 802.11n devices and long-term-evolution (LTE) devices have utilized multiple antennas for providing the MIMO function.
The utilization of multiple antennas, however, may also bring side effects. For example, the signals transmitted from one antenna may be coupled with another antenna and act as noise or interference in the receiving circuit. The coupled signals, therefore, degrade the system performance.
In some devices, the distance between the antennas is increased for reducing the coupling effect. In other applications, isolators may also be used to reduce the coupling effect. As the dimensions of the electronic devices keep shrinking and more elements are built in, the coupling effect becomes even more severe and deteriorates the system performance. Increasing the distance between the electronic elements is not always possible because of the limited physical space of the electronic device. On the other hand, isolators also take a lot of space and are therefore not feasible in many applications. Moreover, isolators often possess a limited bandwidth and may not provide satisfactory isolation.